Switching out a 12-23 cassette to another?

[JeffAngell]

I currently have an ultegra cassette in 12-23 and am looking to switch it out for a 12-25 or a 12-27 (both also ultegra and both to make it easier on steep hills in the Colorado Rocky Mountains). I need a couple tools to get the cassette on and off, is there anything else that I need to be aware of? Will I need to adjust the chain length?

Or is it as simple as changing the cassette with another one and going for a ride?

Thanks for any input.

 

[capwater]

One thing to be aware of is if one cassette is substantially more worn than the newer one. If the old one has worn along with your chain (stretched), the new one may cause shifting problems. Did for me when I put a new one on, new chain fixed the issue. Assuming they are both in the same shape, I believe swapping them should be hassle-free.

 

[JeffAngell]

Originally posted by capwater
One thing to be aware of is if one cassette is substantially more worn than the newer one. If the old one has worn along with your chain (stretched), the new one may cause shifting problems. Did for me when I put a new one on, new chain fixed the issue. Assuming they are both in the same shape, I believe swapping them should be hassle-free.

Thank you. The bike is new (less than a year old) and I am a returning cyclist as I took a little more than 10 years off from road biking. The bike is a litespeed siena with ultegra and then mavic wheels and hubs – I love it and it is great to ride again. I just need a few easier gears than I anticipated for the mountain passes and such – therefore, the reason I am looking to switch from the 12-23 to the 12-25 or 12-27.

Thanks again.

Jeff Angell

 

[daveornee]

Originally posted by JeffAngell
I currently have an ultegra cassette in 12-23 and am looking to switch it out for a 12-25 or a 12-27 (both also ultegra and both to make it easier on steep hills in the Colorado Rocky Mountains). I need a couple tools to get the cassette on and off, is there anything else that I need to be aware of? Will I need to adjust the chain length?

Or is it as simple as changing the cassette with another one and going for a ride?

Thanks for any input.

Maybe simple, but it depends on the condition and length of the existing chain. For the length part:

<http://www.parktool.com/repair_help/FAQchainlength.shtml>

If it was formerly sized by the large-large method.. it will be short.
You obviously don't want to use the "existing chain method".
Check the wear and if it's close to the 1/16" per foot I would suggest starting with a new chain to mate with your new cassette.
Cassette changing tools and methods are covered in another section of the Park Tool repair pages. Lubricating the lockring threads and applying proper torque are key issues.
Also, since there are manufacturing tolerances, you may need a thin spacer to "adjust" for an undesized (width) cassette and/or and oversized cassette body. You want the cassette to sit tight on the cassette body. I also like Park Tool's recommendation of applying a light coat of grease on the entire cassette body.

 

[Bartwick]

From http://www.sheldonbrown.com/derailer-adjustment.html#rear

Most better derailers have an angle adjustment screw (Shimano calls it "B-tension adjustment"). This adjusts the tension of the upper spring of the parallelogram, and thus the height of the jockey pulley. The looser this screw is, the closer the jockey pulley will be to the cluster.

Since you are moving to a bigger cassette, you may have to make an adjustment.

Shimano makes a 13-25 cassette. This gives you a 16 instead of a 12. My bike came with a 12-23 which I had changed to the 13-25. If you're not racing, this may be a smart choice as the 16 is used far more often than the 12.

 

[temoore]

Originally posted by JeffAngell
I currently have an ultegra cassette in 12-23 and am looking to switch it out for a 12-25 or a 12-27 (both also ultegra and both to make it easier on steep hills in the Colorado Rocky Mountains). I need a couple tools to get the cassette on and off, is there anything else that I need to be aware of? Will I need to adjust the chain length?

Or is it as simple as changing the cassette with another one and going for a ride?

Thanks for any input.

For every two teeth, you are adding an inch. As suggested, use the Parktool site.

 

[JeffAngell]

Thanks to all for your help. I did switch from the 12-23 to a 12-27 with no problems. Only had it out on a few rides so far, but all works great and the extra easier gears have made a wonderful difference on a few of the hills so far....


Jeff